2006 July/August - Volume 54 Number 7/8

Papers

Discriminating between speech and music is critical in such applications as speech recognition and automatic music transcription. A new method for achieving discrimination, which is computationally simple, attains almost perfect performance on a wide range of samples. The strategy uses four features extracted from frame histograms: zero-crossing rate, spectral rolloff, perceived loudness, and fundamental frequencies. Modest latency allows the strategy to be used in real-time applications.

Loudspeaker diaphragm vibrations are analyzed in the transitional frequency region where bending waves are beginning to play a significant role in relation to the longitudinal motion. An analytic and numeric analysis shows that the two types of motion are highly coupled. The first nonbending frequency can be considered to be the upper limit of the loudspeaker's frequency response.

Unlike the acoustic simulation of virtual spaces for static environments, with fixed source and listener locations, interactive virtual reality requires the aural experience to match a dynamically changing visual scene. Rapid computations are therefore more important than detailed acoustic modeling of a space. In the approach the geometry of a scene is subdivided into small subdivisions and pre-encoded in optimized data structures, BSP trees, with image source data.

Cumulative Spectral Analysis for Transient Decaying Signals in a Transmission System Including a Feedback Loop(PDF-652KB)
(HI-RES PDF-19.0MB)

Yoshinori Takahashi, Mikio Tohyama, and Yoshio Yamasaki

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Determining the principle resonant frequency of a public address system before the beginning of howling is a valuable tool. By introducing a spectral accumulation function into the previously known technique of cumulative spectral analysis (used with loudspeakers), potential resonant frequencies are more clearly revealed even when they are only barely audible. When applied to the decaying portion of a speech signal, the display clearly predicts the principle resonance. Effectively, the technique increases the order of resonant poles.